In current hydraulic systems, volumetric changes are common resulting from moving parts in the system and temperature changes in the hydraulic fluid. To account for these volumetric changes, current hydraulic systems include a reservoir tank to contain the overflow that occurs as a result of changes in the volume of the fluid.
In any hydraulic system, it is important to prevent the ingestion of air into the system. The entrapment or dissolving of gas into the hydraulic fluid can be problematic. Hydraulic fluid is useful in hydraulic systems because of its incompressible nature. Because gas is compressible, if it becomes entrapped by or dissolved into the hydraulic fluid, the gas can affect the fluid's incompressible nature. If gas comes out of the hydraulic fluid, the hydraulic system may experience pressure drops, cavitation, a loss of functionality, or general harm. As a result, hydraulic systems need to ensure that an inlet or pick-up port of a pick-up tube at the reservoir tank is not exposed to the atmosphere, which would risk the ingestion of air into the system. Hydraulic systems attempt to accomplish this by ensuring this inlet or pick-up port of the reservoir tank is constantly submerged by hydraulic fluid. The pick-up tube may be a tube, pipe, or other elongate body with a hollow portion that allows working fluid to flow into and out of the reservoir tank. The pick-up port may act as an inlet to the pick-up tube to drain working fluid through the pick-up tube.
Certain conventional stationary systems may feature reservoir tanks that allow hydraulic fluid to enter from the top of the tank and exit from the bottom of the tank. Because the reservoir tank does not move, as long as the fluid port is covered by hydraulic fluid, there is little risk of exposing the port to the atmosphere. One may refill the reservoir tank by opening the fill port on top of tank to add more hydraulic fluid. The stationary nature of the reservoir tank allows the tank to be vented to the atmosphere, and no special precautions are necessary when opening the fill port.
However, where the hydraulic system is not stationary, additional precautions may be necessary. In a hydraulic system where the tilting or rotation of the reservoir tank is possible, the shifting hydraulic fluid may expose the pick-up port to the atmosphere.
Current approaches that address this issue involve additional structures and processes in an effort to allow the reservoir tank to tolerate movement. These approaches include pressurized systems and bladder-type systems. Pressurized systems may require specialized tools and equipment to depressurize and re-pressurize the system during repair and maintenance resulting in increased cost, duration, and complexity.
Thus, there is a need for a reservoir tank, tolerant of movement, which does not require pressurization or the use of additional, complex structures that is also easy and inexpensive to manufacture, maintain, and repair.